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Installation and Operation Manual
GG-SO2
SULFUR DIOXIDE GAS SENSOR
2GG-SO2
Warning
Use this product only in the manner described in this manual.
If the equipment is used in a manner not specied by Calibration
Technologies, the protection provided by the equipment may be impaired.
This equipment should be installed by qualied personnel.
GG-SO2 3
Table of Contents
General Description .....................4
Installation .............................4
Locating the Sensor ...................4
Installation Guidelines .................5
Wiring ...............................6
Operation .............................. 7
Start-Up .............................7
Calibration ...........................7
Maintenance ...........................9
Specications ..........................10
Warranty ..............................11
For technical support, contact:
Calibration Technologies
920 N Tradewinds Pkwy
Columbia, MO 65201
866-394-5861
www.ctiengineering.com
4GG-SO2
General Description Installation
The GG-SO2 sensor is a +24 VDC, three-wire, 4/20
mA sensor for sulfur dioxide which utilizes proven
electrochemical sensor technology for fast and
accurate detection. The 0-20 ppm detection range of
the GG-SO2 provides real-time continuous monitoring
of Sulfur dioxide concentrations accurately down to 1
ppm without false alarms.
The GG-SO2 provides an industry standard linear 4/20
mA output signal compatible with most gas detection
systems and PLCs. The output signal is not aected
by drastic temperature and moisture variations that
occur during daily process cycles.
The transmitter circuit board is sealed in potting
compound, protecting sensitive electronic
components and copper tracing from corrosion. The
specially vented chemical-resistant polycarbonate (or
optional stainless steel) enclosure protects the sensor
from accidental damage, weather and direct hose-hits
from clean-up crews.
Locating the sensor
One of the most important considerations when
installing GG-SO2 sensors is that they must be easily
accessible for calibration and maintenance.
Sulfur dioxide is almost twice as heavy as air and
will tend to accumulate in low-lying areas in poorly
ventilated rooms. For optimum personnel protection
(representative concentration reading that an
employee would be exposed to), mount the sensor
at a height no higher than the breathing zone of the
employees. It would typically be about 4 to 5 feet
o the ground, which also allows easy access. As a
general rule of thumb, try to mount sensors within 30
feet of SO2 gas sources.
Caution: Remove protective label.
The sensor is shipped with a label installed over
the gas diusion port of the electrochemical cell to
preserve cell life. The cell will not detect SO2 vapors
with this label installed. Remove label and discard
during installation.
5
GG-SO2
Installation Guidelines:
• Remove and discard protective cell cover
• Always mount the sensor vertically.
• Must be easily accessible for calibration and
maintenance.
• Mount the sensor close to the potential leak source.
• For optimum personnel protection, mount sensor
in the “breathing zone” (5 feet above oor).
• Take air movement and ventilation patterns into
account.
• To prevent electrical interference, keep sensor and
wire runs away from mercury vapor lights, variable
speed drives, and radio repeaters.
• Protect sensor from physical damage (forklifts, etc).
• If mounting on a wall with studs, the mounting
screws should be screwed into the studs.
• Never mount the sensor in CA (controlled
atmosphere) rooms because normal atmospheric
levels of oxygen are required for operation.
• For highly critical locations more than one sensor
should be installed in each room.
• Mount sensor enclosure through the mounting
holes as shown in Figure 1.
2.0"
6.5"
6.8"7.75"
Figure 1: Mounting Dimensions
6GG-SO2
Wiring
Electrical wiring must comply with all applicable codes.
Electrical Power: 24 VDC regulated, 350 mA.
Output: Linear 4/20 mA output. Monitoring
equipment may have a maximum input impedance of
700 ohms.
Cable Recommendation: 20/3 shielded cable
(General Cable C2525A or equivalent). Length of cable
to sensor should be no greater than 1,500 feet.
Monitoring: Monitoring equipment must be
congured to indicate a fault if the signal is below 1
mA. All signals over 20 mA must be considered high
gas concentrations. Alarm setpoints should not be
lower than 10% of full-scale range.
Wiring Guidelines:
• Always use 3-conductor, insulate, stranded,
shielded copper cable.
• Do not pull sensor wiring with AC power cables.
This can cause electrical interference.
• If cable runs cannot be made without a splice, all
splice connections should be soldered.
• Ground the shield at the main control panel.
Connect the shield wire in the sensor terminal
block labeled SHLD.
• Always disconnect power at the controller before
performing any wiring at the sensor.
• To maintain NEMA/IP rating of the enclosure,
conduit ttings of the same rating or better must
be used.
To signal input of monitoring equipment
To +24V terminal of power supply
To ground terminal of power supply
To case (earth) ground of monitoring equipment
Terminal Block Plug (Field Wiring):
SHLD: To case (earth) ground of monitoring equipment
GND: To ground terminal of power supply
+24V: To +24V terminal of power supply
SIG: To signal input of monitoring equipment
Figure 2:
7
GG-SO2
Operation
Start-Up
Allow 60 seconds for power up time delay of sensor
to end (green power LED will ash during power up).
Sensor can be response tested after power-up, but
best to wait 1 hour to zero or span sensor after power
up.
Start-Up Test:
One person exposes each sensor to calibration
gas. The second person stays at the control unit to
determine that each sensor, when exposed to the
target gas, is connected to the proper input and
responds, causing appropriate alarm functions.
LED functions (see Figure 3 on page 8)
Calibration
The GG-SO2 sensor comes factory calibrated and
should require only minimal adjustments after
installation. There are two pots on the preamp that
are used for calibration (see Figure 3).
Note: Never measure sensor output in mA. Always
use mVDC or VDC voltmeter settings.
Zero Calibration: After the sensor is installed and
has been powered up for 1 hour, the unit can be zero
calibrated by the following:
• Be sure the unit is in clean air. If unsure, apply Zero
Air gas at 0.5 to 0.8 L/min.
• Adjust the Zero pot until the sensor outputs 40 mV
from Test [-] to Test [+] (see Figure 3).
Span Calibration: If span adjustment is required, use
the following procedure:
• To enter calibration mode (disables all ltering and
averaging), turn the Zero pot clockwise 1/4 turn and
then back again. Successful entry into calibration
mode will be indicated by the Power (green) LED
blinking twice per second. Calibration mode will
time out automatically after 4 minutes.
• Apply span gas at 0.5 to 0.8 L/min (span gas must
be in air, not nitrogen or other carrier).
• Sensor should react to gas within 15 seconds.
• Once the output signal has peaked (or 3 minutes
maximum) adjust the Span pot until the correct
output is achieved (see Figure 3). With full-scale
span gas, the calculated span value is 200 mV.
((span gas / sensor range * 16 + 4) (mA output))
Note: Below are a few response characteristics which
may be an indication that the gas sensor is at or near
the end of its useful life. If any of these are observed,
the cell should be replaced:
• Slow response to / recovery from calibration gas.
• Failure of the output to reach 50% of the calibration
gas value prior to span adjustment if last calibration
was 6 months ago or less.
• Unable to achieve correct output during span.
8GG-SO2
Figure 3: Sensor board components and zero/span adjustment
Sensor Cable plugs into socket here
Span adjustment
Zero adjustment
40-200 mV
mVDC
Black Red
-+
Fault (red) LED:
• On steady if supply voltage is
less than 10VDC.
Status (amber) LED:
• Blinks once per second if RFI is
detected.
Power (green) LED:
• On steady to Indicate Power.
• Blinks once per second for 60
seconds during power-up.
• Blinks once per second
continuously if supply voltage
is too low.
• Blinks twice per second in
calibration mode (4 minute
timeout delay).
Cell
9
GG-SO2
Maintenance
The GG-SO2 was designed for long life and minimal
maintenance. For proper operation it is essential
that the test and calibration schedule be adhered to.
Calibration Technologies recommends the following
maintenance schedule.
Maintenance Guidelines:
• The sensor is shipped with a factory calibration.
Sensor should be calibrated 6 months from
purchase date.
• Calibrate the detector at least once every 6 months.
• Calibration should be performed with certied
calibration gas. Calibration kits and replacement
cylinders are available from Calibration
Technologies.
• All tests and calibrations must be logged.
• Always disconnect power at the controller before
performing any wiring at the sensor.
Sensor Life:
These electrochemical cells are extremely reliable, but
several things can cause the cell chemicals to become
depleted including:
• a period of time
• exposure to high temperatures
• continuous, long term exposure to sulfur dioxide
When the cell becomes depleted, the unit will give no
indication of failure other than that the sensor will not
respond. For this reason, it is absolutely essential
that these sensors be calibrated on a regular basis.
Typical cell life will be two to three years. When the cell
becomes depleted, a replacement cell can be obtained
from Calibration Technologies. Simply unplug the cell’s
ribbon cable from the transmitter, pull the old cell
from the spring clip, discard the old cell and replace it
with a new one.
Replacement cell order #:
GG-SO2-RC
10 GG-SO2
Specications
Input Power: +24 VDC, 350 mA
Detection Principle: Electrochemical
Detection Method: Diusion
Gases: Sulfur Dioxide (SO2)
Ranges:
0/20 ppm (standard)
Output Signal:
Linear 4/20 mA (max input impedance: 700 Ohms)
Response Time:
T50 = less than 30 seconds
T90 = less than 90 seconds
Accuracy:
+/- 5% of full-scale, but dependent on calibration gas
accuracy and time since last calibration
Zero Drift: Less than 0.1% of full-scale per month,
non-cumulative
Span Drift: Application dependent, but generally less
than 3% per month
Linearity: +/- 0.5% of full-scale
Repeatability: +/- 1% of full-scale
Temperature Range:
-40°F to +122°F (-40°C to +50°C)
Humidity Range: 5% to 100% condensing
Dimensions: 7.7” high x 6.7” wide x 3.8” deep
Weight: 3.0 lbs
Power (green) LED: Blinks once per second for 60
seconds during power-up. If supply voltage is too low
(<10VDC) or improperly grounded, will blink once
per second continuously. Stays on steady to indicate
power. Blinks twice per second in calibration mode
(4-minute timeout delay).
Status (amber) LED: Blinks once per second if RFI
(radio frequency interference) is detected.
Fault (red) LED: Stays on steady if supply voltage is
too low (<10VDC) or hardware failure.
Wiring Connections: 3-conductor, shielded, stranded,
≥ 20 AWG cable (General Cable C2525A or equivalent)
up to 1500 ft.
Terminal Block Plug (Field Wiring): 26-12 AWG,
torque 4.5 lbs-in.
Enclosure: Injection-molded, NEMA 3RX washdown-
duty, polycarbonate sensor housing with hinged lid
and captive screw. For non-classied areas.
Optional 18 GA, NEMA 3RX washdown-duty stainless
steel enclosure with hinged lid and captive screw. For
non-classied areas.
Certication:
SGS Listed:
Conforms to UL 61010-1
Certied to CSA C22.2 No. 61010-1
11
GG-SO2
Limited Warranty & Limitation of Liability
Calibration Technologies, Inc. (CTI) warrants this product to be free from defects in material and workmanship
under normal use and service for a period of two years (including the cell), beginning on the date of shipment
to the buyer. This warranty extends only to the sale of new and unused products to the original buyer. CTI’s
warranty obligation is limited, at CTI’s option, to refund of the purchase price, repair, or replacement of a
defective product that is returned to a CTI authorized service center within the warranty period. In no event shall
CTI’s liability hereunder exceed the purchase price actually paid by the buyer for the Product.
This warranty does not include:
a) routine replacement of parts due to the normal wear and tear of the product arising from use;
b) any product which in CTI’s opinion, has been misused, altered, neglected or damaged by accident or abnormal
conditions of operation, handling or use;
c) any damage or defects attributable to repair of the product by any person other than an authorized dealer or
contractor, or the installation of unapproved parts on the product
The obligations set forth in this warranty are conditional on:
a) proper storage, installation, calibration, use, maintenance and compliance with the product manual
instructions and any other applicable recommendations of CTI;
b) the buyer promptly notifying CTI of any defect and, if required, promptly making the product available for
correction. No goods shall be returned to CTI until receipt by the buyer of shipping instructions from CTI; and
c) the right of CTI to require that the buyer provide proof of purchase such as the original invoice, bill of sale or
packing slip to establish that the product is within the warranty period.
THE BUYER AGREES THAT THIS WARRANTY IS THE BUYER’S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF
ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. CTI SHALL NOT BE LIABLE FOR ANY SPECIAL,
INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES, INCLUDING LOSS OF DATA, WHETHER
ARISING FROM BREACH OF WARRANTY OR BASED ON CONTRACT, TORT OR RELIANCE OR ANY OTHER THEORY.
ctiengineering.com | 866-394-5861
GG-SO2-DOC1-3
20211103
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